The Serena Williams' farewell tour in Toronto is over after she was knocked out of the Canadian Open 6-2 6-4 by 12th seed Belinda Bencic on Wednesday.
Williams, playing for the first time since declaring on Tuesday her intention to retire after this month's US Open, was no match for Tokyo Olympics gold medalist Bencic.
The 23-time major winner was unable to claim back-to-back WTA singles wins for the first time since last year's French Open, having defeated Nuria Parrizas-Diaz for her first victory in 430 days on Monday.
Bencic triumphed in one hour and 17 minutes, winning 84.2 per cent of first-serve points and converted five of eight break points throughout the match.
Williams' power was on show with 13 winners, but Bencic was physically more capable and decisively managed 25 winners with only 13 unforced errors.
Elsewhere, 2019 US Open winner and local hope Bianca Andreescu edged Alize Cornet in a see-sawing clash in the evening, winning 6-3 4-6 6-3 in two hours and 26 minutes.
Fourth seed Paula Badosa and fifth seed Ons Jabeur, who was last month's Wimbledon runner-up, were forced to retire due to injury.
Spanish 24-year-old Badosa withdrew against Yulia Putintseva 7-5 1-0 due to muscle cramping, while Zheng Qinwen had a walkover against Jabeur 6-1 2-1 due to abdominal pain.
Top seed Iga Swiatek brushed aside Ajla Tomljanovic 6-1 6-2 in 64 minutes. The win means Swiatek is the first player to win 15 WTA 1000 matches in straight sets in a row since 2009.
Canadian 13th seed Leylah Fernandez also bowed out, going down 7-6 (7-4) 6-1 to Brazil's Beatriz Haddad Maia, who will face Swiatek in the third round.
Second seed Anett Kontaveit lost 6-4 6-4 to Jil Teichmann in one hour and 27 minutes. Teichmann will next face Simona Halep who won in 71 minutes against Zhang Shuai 6-4 6-2.
Sixth seed Aryna Sabalenka got past Sara Sorribes Tormo 6-4 6-3 to set up a third-round meeting with Coco Gauff after she defeated Wimbledon champion Elena Rybakina 6-4 6-7 (8-10) 7-6 (7-3) in an epic that lasted two hours and 49 minutes.
Jessica Pegula won 6-2 7-5 over American qualifier Asia Muhammad to progress through to face Camila Giorgi after she knocked off Elise Mertens 7-3 7-5.
Third seed Maria Sakkari triumphed in three sets 6-2 4-6 6-2 over Sloane Stephens and will face Karolina Pliskova next after the Czech beat Amanda Anisimova 6-1 6-1.
Eighth seed Garbine Muguruza won 6-4 6-4 against Kaia Kanepi and Alison Riske toppled 16th seed Jelena Ostapenko 7-6 (7-2) 0-6 7-5.